Drift sight



D. L. WEBSTER AND H- N. RUSSELL.

DRIFT SIGHT.

APPLICATION FILED JULY29, 1919.

1,436,924. Patented Nov. 28, 1922.

2 SHEETS-SHEET I.

D. L. WEBSTER AND H. N. RUSSELL. mun smm.

APPLICATION F|LEDIULY29,\919. 1,436,924. Patented Nov. 28, 1922.

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PM Nov. 2a, 1922.

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Be it known that we, Devin L. Wm and Hmmr N. Rusenu ncitlzens of the United States, residing at Norfolk, State of usetts an Princeton, county of Mem,,sem of Nev tgfileyayg Jersey, reepeetivel ,have invented 'certe'mnew and useful improvements in gights, ofwhich the followlng is o 8P00lfl8 1011. I

This retely determining and aiding time for; the drift of an e'u'plane or other dim-ft due to cross winds. The ut lity of a device ofthis character, or adrift es it me be termed, is two-fold. First, given a. efimte compass course-to be eetil oily made good over $2 go't'a fi. m 3m in e anem'oun U ing on thewind. I e wind isnnknown, a previous calculation of the course to" steered is im' ssible. Evemit. known, ,a correct ealc tion would nsuall have to iellow forehangeeinth st d motion the wind time end m thefrere 09'0" eugu orm wind, the correlation for'dnit qsurfile sight is m praotioeeasier than ate r calc tlon. Second, thedrift eightmey he need in eheoldng e'mree by landmarks id b f 0 m When he use it" is, a that the eight beeombined' Wlflt l; or direction mdieetor'oapehle of xi an object lying quite a. dietanmon ther of the nose of the ship, geiiebout 40 or d The m 0 than he used as a mark for over. In the present invention,

indimtor'is a. part of-the itselfond does not involve any sewnd' ejustment It is the purpose of this inyent onto over-1 come the several eourees'of BB1 of ments. These prin ally 6s follows:-

Bum y win-In order to over'oome the efiects o bmnpy air, which renders the e pvg'ent mot on otthe-learth i gq r," e

countered in the invention relates to means for ecen in the correce ground, theeourse' be drift but net iloting the air, the 1s to uneonsoiou y begin/tojudgethe ,the ship by the ob eet the reference mo: em

ltheehl will soonhe' Sign; brocess. If the e ed nm. em Io. new.

a of the drift indicator on .w j,meesurement is taken must be ion on 11 so that a. single ob'ect on the gronn gniy folloyed for sue a distance that apparent notion .of the ie'inedue to rollin w ll be neutralized t rolling be will, and all such effects wil eve'mge out.

ls-nleloes lt 'verydiflionltto get good re. 00 eultembuxnpyurwatharefereneelin e m the form of a; wire of such length" that it can be set in a revolving eireieand still be far eno from the bperators eye to be in focus. t 15 however,to use a. wire sevoseral teet long if possible. Even with such is below about one thoneand feetof nltitude. v

810w romn or gonuing.-The efleet of slow rollingo the au'jrlene, which gives an 10 epparent'motion that is steady for short intervals but in the. wrong direction is not troubmome to an'oheerver the In oting h ev h e we p t q fi the reen? i gives etenden"toroll so theehl insuoheweyaetdmeke: e'obiect more ong the reference line and eiell'y'in l efieet ie'inore'aeed by .the yei e fo l of sense of'balenee on tippin hie head for 86 ward' to 'look down towardv 61- o'eliminato tho 1 t I o set the direction of the indicatwire on that angle and the ship level, and use the eilerons-so as to, melee the ob- 16011 d ng thewire. If the guess was to have roll-is to v 1' swinging endof the 1nd; n wire should be moved to the rlglili for thenext trial and the process Side a.lin;-C'onsidei'ation of variable emounh; of e1 de slip duejoleek of level of the ehip'durmg thed'rl-ft meesurementor me an flying the course determined, is quite important. It is best of eourse, in "order to obtain accurate meas'urements,to keep the level end the ship heed d so as to gape-.15

kept on. the same latersllevel make the proper track. But whether this is done or not, the drift angle will not be the some at different times unless the lateral.

must lb: ring t the rest of the level is the same. Hence the Silk) u .wind, but are quite important in a. strong d 'e lfii' eh b 11 a e anges y cents as the speed but increases when the nose 0 In-suehceses on the average the hhout the same perdecreases. The air speed should eretfore be kept fairly constant during the Images a wind dm'mg' ht-Suchat al des'gseful in as country work, especially if the wind is strong, are

common enough tomake serious errors'i.

Consequently, the drift "should be meashred often eno'ug during a flight to prevent sucherrors.

Other and further objects of the invention will apgoear as the nature of the same is better un rstoed from consideration of the following description taken in conjunction withthe drawings, representing a. preferred embodiment o the invention, and in which like numerals indicate the same parts,

Fi a a clearly the throughout the several views.

Fig. 1 represents a front elevational view of an airplane showing my invention as ap-. p d thereto,

' 2 a sectional view taken on line 2-2 F offerspeetive-view showing more once as it appears on one side of the machine, and

Fig. 4 a view taken from an airplane in fli t the device in use.

tothedraitwillbeseen that l8 dufilic .5 On of the 01 is either side e airp no. is angrlle of drift may be taken on either side of t eairplane whether the machine be to one side or a; the other. The device on one side of the fuselage only will be described this descri ption applying equally to the evice on the opposite side. A slghtin wire 1 is suspended between the 11 per 'ft stay that is the one running in the nose 0 the. ship to the upper wing and the upper I acelif thelower" wing adjacent the fuselage. Here it'passes through a screw eye 2, or some similar device, secured on the upper face of the wing di e y n er the p we Where the pilot '-may be rigged.

"would most naturally place eye on leanstay. ,In the ordinary type of machine, this would locate sighting wire 1 at a slant of about 45'-de In order to maintain the sighting wire taut, the end th which projects through screw eye 2 en spiral 4 which is astened of the us dfitge at 5. Means 1. inthe form-ofa line 6 running fixed pulleyl 7 on the nose of the ship and back to a cleat 8, or other suitablemeans, in the cock pit, whereby pulley 8, and thus sight' wire'l, can be-p I led in toward the the slug. Thus, line 6, acting in conjunction wit the tension exerted by spring 4, afi'ords means for adjusting-sightingwue 1 from nearly zero an is with the fuselage, or the fore and aft of the maohin to about 30 de rees or so from it, at will int the ting wire becomes perpendlc ar to the dnft stay. In order to move the sighting were out beyond number of degrees alforded at the owner:- tioned perpendicular position, an outhaul This arrangement how-' ever would rarely be needed in high a eed machines and then onl'y'in strong win s. Radiating from screw eye 2 and on the upser surface of the lower wing, therein prov: ed a series of lines arranged at uniform angle intervals and placed with 'referenceto e fore and aft line of the machine. Directly over screw eye 2 and adjacent the edge of the cock-pit of the machine, is a button 9,-

head over 'the si e of 'the fuselage toward which he is with his e e apprenmately 0V3; the rgar b5: eurac' ineposi ion'o e eisreqmred The then setssightiiig wire 1 so that, at a rough guess, the movement of the ground below to coincide with the wire when he h'eadstheeourse he must take. A reading of the angle indicated the sigh wire on the scale on the wing is,- then n, following which the compass is corrected. by the same amount. For 'example, if it is desired to make a course of two hundred and thirty degrees (to the right from north) and this first estimsteof the drift is fifteen degrees to the then the course should be altered to two undred and using the sighlgthe observer leans his 0 great are-.14

fifteen degrees. The drift is now liable I was merel a rough es no time is lost. The observ er then me s: a better determination, sets th sighting wire to the best 1 theuse of a long sighting wire.

- of his drift with the wings to tlm horizon and sometimes above it, th

he can make, sets the ship propler air speed; and then holds the ship so t at tbe'hne of the s ghting wire on the round stays fixed, except for bumps, on two objects on the ground that lie on it, as shown in Fig. 4. I the estimate is wrong, this process results in the pilot rolling the ship one wa or the other in an effort to hold the line 0 the wire fixed. If he rolls to the right, he moves the sightin wire to the *ht, sets the ship level an tries again.

1th the new drift thus determined, h rects his compass readin again. In the example given above, if his new drift is say twelve degrees to the right, his new course will be two hundred and eighteen degrees. Theoretically, the cha from two hundre and fifteen to two hun red and eighteen de- 9 should change the drift again but practically, if the first guess is good for the second change is too small to measure in almost every case. The one precaution he must observe is to start each test of the ship level and ing straight ahea at the speed he inten s to hold.

Thus, having set the course by use of the drift sight, the pilot may very readily use it to ho d the course and prevent errors due to changes of wind, that the line of the si hting wire. from over the back sig t 9, extends nearly us showin him just what y over. c then picks a distant land mar that lies on the sighting wire with his eye over the back sight 9, and looks at the object every few minutes in order to be sure it is still on the wire. If it isnot, his drift measurement is wrong or else the wind has changed, and he .must therefore set the sighting wire to a slightly different n is and change his course accord objects he will 11 ingly. is type of readjustment is the source of the extreme accuracy of this method of crosscountry flying, and depends primarily on Even if the air should be too umpy for an accurate measurements by objects nearly low, this type of adjustment can still be made quite easily.

in its prefer or plan and The accuracy obtainable with the sight in steering cross-country courses is about one degree, or steering by aid of the sight in strong variable winds, the airplane can made to follow, a course without leaving it by more than one mile in traveling sixty.

Although the invention has been shown red form and the details of con-, structlon thereof described more or less preciscly, it is to be noted that any form of apparatus which utilizes long reference lines, either in the form ofwires or partly wires and partly other marks on the aireither fixed or movableand s dead level at the by reason of the fact ing placed that they objects at consider'able distances air plane as well as nearer to it, would answer the same urposes; further, that. it is not intended t at the scope of the invention be limited to the construction shown, as changes in form, the proportion of parts, as circumstances may suggest or render expedient, may be made without departing from the spirit of the invention.

Although the sight has been being use from the desired to state that t e same may? in any ition on an airplane or other" aircraft from which it is desired to determine the angle of drift.

What we claim is: 1. A drift indicating device for aircraft, comprising in combination with a bi lane, having a fixed angle-measuring gra uated surface, a rear sight, and a direction indicating element extending from a point in line with said sight and adapted to be moved over said graduated surface and brought into coincidence with the path of flight of the craft.

comprising having a fixed an m the drift indicating in combination with a 23310110 le-measuring gr uated surface, a rear slg t, a direction indicating element extending from a point in line with said sight and adapted to be moved over said graduated surface and brought into coincidence with the path of flight of the craft, and means for swinging said indicatelement about said point. i

3. A drift indicating device comprising in combination with a biplane, a rear sight, a flexible direction indicating element extending from-a point in line wit said sight and adapted to be brought into coincidence with the path of flight of the craft, means for swinging said indicating element about said int le measuring means associated wit sai' sig t, and means for holding said direction indicating element taut.

4. A drift indicating device for aircraft, comprising in combination with a biplane,

and the substitution of equivalents,

can be used in sighting device as aircraft,

a rear sight, a sighting wire connected for a in relation to said graduated surfac and means for shifting the movable end of said sighting strip. 6. An aircraft having on a fixed surface thereof angle measunng lines radiating 5 from a common point, a sighting stri having one end attached to the aircraft in line with said point, and means for shifting the eidence with the pat other end of said si hting strip into coinof flight of the aircraft.

In testimony whereof we aflix our'signatures. I

DAVID L. WEBSTER. HENRY N. RUSSELL. 

